1. Field of the Invention
The present invention relates to semiconductor structures, and more particularly to semiconductor package structures and method for forming the package structures
2. Description of the Related Art
With advances in electronic products, semiconductor technology has been applied widely in manufacturing memories, central processing units (CPUs), liquid crystal displays (LCDs), light emitting diodes (LEDs), laser diodes and other devices or chip sets. In order to achieve high-integration and high-speed requirements, dimensions of semiconductor integrated circuits have been reduced and various materials, such as copper and ultra low-k dielectrics, have been proposed and are being used along with techniques for overcoming manufacturing obstacles associated with these materials and requirements. Further, package techniques incorporating with small-dimension integrated circuits would provide desired chip packages.
FIG. 1 is a cross-sectional view of a traditional package structure. The package structure 101 includes solder balls 120 bonded on substrate 110. The substrate 110 with the solder balls 120 is then flipped and mounted on substrate 100. After the mounting step, an under-filler material 130 is filled between the substrates 100 and 110, protecting the solder balls 120 from particle contamination and electrically isolating the adjacent solder balls 120. The underfill also provides mechanical support and helps prevent failure of the solder joints.